Ink jet printers are capable of producing multicolored ink drawings and printings of various type or kind. Ink jet printer heads scan the entire surface of a paper sheet and tiny droplets of ink are deposited on the sheet in the areas designated by a central control.
An ink jet printer is capable of depositing these droplets in any or all of several hundreds of thousands of designated positions on a single sheet of paper in a single pass of the ink jet heads. It is able to do this in a practical and efficient manner by the application of a sophisticated electrical system that precisely signals the printer heads when to deposit the ink droplets. The heads very rapidly pass over the designated positions on the sheet and there is only a fraction of a second available for depositing the ink droplet. The electronics can rapidly identify the designated positions and accurately generate the electronic signals. The major problems that have to be overcome are generally in the ink flow system.
The ink jet heads use piezoelectric crystals that respond to the electronic signals and function like tiny diaphram pumps that pump the ink droplets out through the ejecting outlet of the head. An air supply can be introduced at the outlet to accelerate the ink ejection. Ink flow is interrupted after each pumping stroke of the crystal simply by the meniscus that forms within the outlet opening.
It will be appreciated that the ink flow system including the outlet is minute and special inks are required to satisfy the system's specifications. Most important is the requirement that the ink be free of bubbles and impurities. Even a small fleck of dirt can lodge in the outlet and clog it. An air bubble is compressible and the pressure of the piezoelectric crystal will be absorbed by the bubble and the system will fail to eject the ink droplets.
Whereas special formulas of ink and sterile mixing and bottling techniques can insure the purity of the ink source, a major problem is introduced when maintenance is required for the system. For example, it may be necessary to replace a head. The ink flow lines have to be disconnected from the old head and reconnected to a new one. Instead of the sterile surroundings in the factory, this job is done at the operating site and, invariably, bubbles and/or other impurities get into the system.